The present invention relates to an automatic focus adjusting system that can be applied to a camera or the like, and relates, more particularly, to an automatic focus adjusting apparatus and an automatic focus adjusting method capable of adjusting a focus of a moving subject.
Among techniques developed in recent years for a focus adjusting of an optical apparatus, there has been disclosed in U.S. Pat. No. 5,208,625, for example, a technique for detecting a move of an image of an image picked-up subject on a line sensor in an example of an automatic focusing apparatus having a focus detector based on a TTL phase difference detecting system.
In a camera built in with such an automatic focusing apparatus, it is judged whether or not an image picked-up subject has moved during a predetermined period of time, based on an image picked-up position of the subject at a certain time and an image position of the subject after a lapse of the predetermined period of time. When it is judged that the subject has moved during this period, the focus of the moved subject is adjusted to a correct focus based on a speed at which the subject moved.
This focus adjustment is what is called a "moving body correction" that is carried out as follows. When a move speed of an image of the subject on the line sensor is higher than a speed of a predetermined value when the subject has moved, it is judged that the subject is a moving subject, that is a moving body. Then, an image screen position of the subject at the time of starting an exposure is predicted based on a release time lag.
According to the above-described prior-art automatic focus adjusting apparatus, however, an obtained image of the subject may have deviated from the line sensor, when the subject has moved up and down or when the camera has moved due to a touch on the camera by hand or the like.
Accordingly, there may be a low correlation between image positions of the subject during a predetermined period of time, and thus there arises a situation where it is not possible to accurately detect the moving body.
As a result, there may be a case where a moving body is regarded as a stationary body, and the image of the moving body is not focused completely, thus producing a blurred picture.